1. Field of the Invention
This invention relates to an ear speaker device, and is desirably applied to a head-mounted wearable speaker device.
2. Description of the Related Art
As a headphone device being one example of a head-mounted wearable speaker device, there are widely diffused devices which are mounted to the head of the listener, and convert an audio signal representing a reproduced sound etc. of a compact disc (CD) to a sound (referred to as reproduced sound, hereinafter), and make the listener listen to the reproduced sound.
In the headphone device generally used, a speaker unit that generates the reproduced sound is positioned in the vicinity of the front of an entrance of an external acoustic meatus of the listener. Although a sound is allowed to reach an eardrum directly from the speaker unit to possibly improve sound quality, a sound image is localized in the head of the listener and this has provided an unnatural impression to the listener.
For the above reason, there has been devised the headphone device in which the speaker unit is positioned at a location somewhat distant from the entrance of the external acoustic meatus (ear hole) and closer to a parietal region. In this manner, the sound image is localized outside the head just like a general stationary speaker to remove the unnaturalness. At the same time, the headphone device is made as a closed type to form enclosed space around an ear of the listener in consideration of making the listener capable of listening to a low-pitched sound sufficiently (For example, refer to Jpn. Pat. No. 3054295 [page 3, FIG. 1]).